SMT 1 nF capacitor in parallel with the coil, for tuning it to approximately 125 kHz

Sealed with clear packing tape on the opposite side

It’s ugly, and I really want to try this experiment over again with a smaller IC package, like TSSOP-8. But the card works very well, and the read range is practically indistinguishable from a mass-produced RFID card. I tested this one using an official HID ProxPoint reader.

I’ve been busy, but once I have time to perfect this technique I’m hoping to write some instructions, as it’s a pretty quick and easy way to make a DIY RFID tag that’s actually in a convenient form-factor.